High-current switch with contact pressure booster

ABSTRACT

A high-current switch comprising two fixed terminals of rectangular tubular construction each having its top wall cut away to afford a pair of fixed contacts at each terminal, and two dual-blade movable contact members, each pivotally mounted on one fixed contact of the first terminal and conjointly pivotally movable into pressure contact with the opposed sides of a fixed contact of the second terminal. The free ends of the two inner contact blades project inwardly into close proximity with each other to function as a unitary structure and to preclude distortion of the blades when the switch is opened under overload or closed under fault conditions; the inward extensions of the inner blades carry arcing contacts aligned with fixed arcing contacts on the second fixed terminal. A single arc chute may be mounted on the outer walls of the second fixed terminal, encompassing the paths of the free ends of all of the contact blades in the region just above the second fixed terminal.

United States Patent [191 Erickson 541 HIGH-CURRENT SWITCH WITH CONTACT PRESSURE BOOSTER [75] Inventor: John W. Erickson, Crystal Lake, Ill.

[73] Assignee: Erickson Electrical Equipment Co.,

Chicago, Ill.

[22] Filed: Nov. 22, 1971 [21] Appl. No.: 200,713

[52-] US. Cl. ..200/170 A, 200/48 KB [51] Int. Cl. ..H0lh 1/50 [58] Field of Search...200/l70 R, 170 A, 166 E, 162,

. 200/48 KB, 144 R [561 References Cited UNITED STATES PATENTS 2,960,590 11/1960 Kussmaul et a1 ..200/162 X 3,441,699 4/1969 Erickson ..200/144 R 2,824,938 2/1958 Rugg et al. ..200/162 3,410,974 11/1968 KussmauL. ..200/170 A X 3,118,032 l/l964 Davis ..200/170 A X 3,064,107 11/1962 Date ..200/170 A 3,180,963 4/1965 Hales et al. ..200/170 A Jan. 2, 1973 Primary Examiner-H. 0. Jones Attorney-James B. Kinzer et al.

57 ABSTRACT A high-current switch comprising two fixed terminals of rectangular tubular construction each having its top wall cut away to afford a pair of fixed contacts at each terminal, and two dual-blade movable contact members, each pivotally mounted on one fixed contact of r the first terminal and conjointly pivotally movable into pressure contact with the opposed sides of a fixed contact of the second terminal. The free ends of the two inner contact blades project inwardly into close proximity with each other to function as a unitary structure and to preclude distortion of the blades when the switch is opened under overload or closed under fault conditions; the inward extensions of the inner blades carry arcing contacts aligned with fixed arcing contacts on the second fixed terminal. A single arc chute may be mounted on the outer walls of the second fixed terminal, encompassing the paths of the free ends of all of the contact blades in the region just above the second fixed terminal.

4 Claims, 2 Drawing Figures damage HIGH-CURRENT SWITCH WITH CONTACT PRESSURE BOOSTER CROSS REFERENCES TO RELATED PATENT The present invention utilizes the arc control apparatus of U.S. Pat. No. 3,441,699 to John W. Erickson, adapted to utilization with a switch using two dual-blade movable contact members.

BACKGROUND OF THE INVENTION With increasing electrical loads in both housing and industrial buildings, particularly apartment houses and manufacturing plants, there has been a substantial tendency toward increased current rating requirements for service entrance switches. In particular, the necessity for provision of service entrance switches rated up to 6000 amperes is quite common, in comparison with utilization of substantially lower ampere ratings in the past; These switches must be capable of handling currents within their rating with no overheating and with little or no arcing; they must also be capable of opening under heavy overloads with limited arcing and no substantial damage to the switch. Further these switches must be capable of closing under fault conditions without endangering personnel or equipment in the immediate area of the switch.

Merely increasing the size ofthe conductors and other elements in service entrance equipment designed for lower ampere ratings is not a satisfactory design basis for high capacity service entrance and similar switches. Mere up-grading of previous designs results in switches that are excessively large in size, particularly with respect to the arc suppression apparatus, but also in regard to other switch components. Frequently, the switches are excessively heavy and are subject to blade when opened under fault conditions. Moreover, overheating often occurs.

One proposed modification for switches of this general kind that is useful for high ampere ratings entails the utilization of tubular conductors for the input and output connections of the switch, as shown in Kussmaul et al U.S. Pat. No. 2,960,590 and Burt et al U.S. Pat. No. 2,845,512. This preliminary step in the right direction, however, does not solve the difficulty of affording adequate arc suppression, in a compact size, for the interruption of overload currents in a switch of this capacity. Moreover, the dual double-blade switch construction shown in those patents may be damaged, when the switch is closed under fault conditions, with the inner switch blades being bent toward each other as a resultof the extremely large electromagnetic forces to which the switch is subjected.

SUMMARY OF THE INVENTION It is a principal object of the present invention, therefore, to provide a new and improved switch, suitable for operation at currents up to 6000 amperes and even adequate arc protection for a high capacity load break switch, at less expense and with smaller space requirements than previously possible.

Another object of the invention is to provide a load break switch suitable for applications requiring current rating of the order of 6000 amperes that is cooler in operation and that is capable of absorbing the large forces applied to the switch when closed under fault conditions or opened during an overload without substantial damage to the switch. A particular feature of the invention in achieving this objective is the utilization of a construction that allows location of arcing contacts. for the switch at about the same level as the main switching contacts, affording a highly compact construction for the switch.

Accordingly, the invention relates to a high current switch, particularly suited for service entrance and like applications in which the switch may be opened under overload or closed under fault conditions. A switch constructed in accordance with the invention comprises a first fixed terminal and a second fixed terminal mounted on a base in spaced relation to each other, each fixed terminal comprising a tubular conductor of generally rectangular configuration having a portion of its top wall cut away to afford a pair of fixed contacts extending toward and aligned with a similar pair of fixed contacts at the other terminal. The switch further comprises two movable contact members each comprising a pair of contact blades pivotally mounted at one end on opposite sides of one fixed contact of the first terminal with each movable contact member being movable along an arcuate path between an open position displaced from the second terminal and a closed position in which the free ends of the contact blades engage substantial areas in opposite sides of a fixed contact at the second terminal. The inner contact blade of each movable contact member includes an integral extension, at the free end of the blade, projecting inwardly toward and into close proximity to the corresponding extension portion on the inner contact blade of the other movable contact member. These extension portions carry the movable arcing contacts of the switch. An operating mechanism is provided for moving the movable contact members, conjointly, between their open and closed positions and for tightly clamping both blades of each contact member to the associated fixed contacts when in the closed position. An arc chute is mounted on the second fixed terminal, the arc chute comprising two side frame members mounted on opposite side walls of the second fixed terminal with a back wall mounted between the frame members to afford a frame encompassing three sides of an arc space along a part of both of the movable contact member paths immediately above the fixed contacts of the second terminal. A plurality of grid plates extend across the frame between the two side frame members to form a plurality of arc-dividing chambers within the aforementioned arc space. The fixed arcing contacts of the switch are mounted on the same level as the top of the second fixed terminal.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a plan view of a single pole for a high-current load break switch constructed in accordance with the present invention, with a part of the apparatus cut away to reveal internal construction; and

vFIG. 2 is a sectional elevation view taken approximately along line 2-2 in FIG. 1.

' DESCRIPTION OF THE PREFERRED EMBODIMENT FIGS. 1 and 2 illustrate a single-pole high-current switch 10, suitable for service entrance and like applications in which the switch may be opened under overload or closed under fault conditions, and having a current rating of up to 6000 amperes or even higher. Ordinarily, switch would be mounted in a two, three, or four-pole assembly, with all of the switch poles connected to a common operating mechanism for simultaneous operation in opening or closing the switch. Inasmuch as the other poles of such a switch assembly would be constructed in the same manner as the single pole switch 10, there is no necessity to illustrate additional poles for the switch.

Switch 10 comprises a first fixed terminal 11 mounted on an insulator base 12 by suitable means such as a plurality of bolts 13 (FIG. 2). Terminal 11 is a segment of a tubular conductor of generally rectangular cross-sectional configuration having a top wall 14, side walls 15 and 16, and a bottom wall 17. A portion of the top wall 14 of terminal 11 is cut away as indicated by reference numeral 18 in FIG. 1 to afford a pair of parallel fixed contacts 21 and 22 extending toward a second fixed terminal 23. The second fixed terminal 23 is mounted upon base 12 by suitable means such as the bolts 24 (FIG. 2). Terminal 23 is also formed froma segment of a tubular conductor of generally rectangular configuration, having'a top wall 25, side walls 26 and 27, and bottom wall 28. A portion of the top wall 25 of terminal 23 is cut away to afford a pair of parallel fixed contacts 31 and 32 aligned with and extending toward the fixed contacts 21 and 22, respectively, of the first terminal 11.

Switch 10 is provided with two dual-blade movable contact members, one for each aligned set of fixed contacts. The first movable contact member 33 comprises an outer contact blade 34 and an inner contact blade 35. The contact blades 34 and 35 each have one end pivotally mounted upon the first fixed contact 21 of the first switch terminal, the two blades being disposed on opposite sides of fixed contact 21. The pivotal mounting is afforded by a bolt 36 that extends through contact 21 as well as blades 34 and 35, and is freely rotatable therein. Bolt 36 is threaded into a nut 37 mounted upon the outer contact blade 34. The head 38 of bolt 36 is welded to a crank 39. Crank 39 is of L- shaped construction, with the free end of the crank terminating in a flange 41 connected to an operating bar 42 which is in turn connected to an operating mechanism for the switch. The operating mechanism, which may be of one of the types shown in US. Pat. Nos. 3,213,247, 3,522,401, or 3,582,595 to M. Stene, has not been illustrated in the drawings. In FIG. '1, flange 41 has been cut away to give a better view of other elements in the switch mechanism.

Crank 39 is a part of a toggle mechanism that includes a dual toggle link 43 having one end pivotally 34 and 35 carries a spacer 49 that is received in a slot 49 in the fixed contact 31 when switch 10 is closed.

The toggle mechanism for operation of switch 10 further includes a spring 51 having one end connected to link 43 and having the other end connected to a pin 52 mounted on movable contact blade 35. A toggle break post 56 is mounted on base 12 in alignment with toggle lever 43. A spacer 53 is mounted between blades 34 and 35, in the central portions of the two blades, on a pin 54 that extends between the two blades and carries a spring 55 biasing the two blades toward each other and into engagement with spacer 53.

Switch 10 further comprises a second movable contact member 63 comprising two movable contact blades 64 and 65. Each of the two movable contact blades 64 and 65 is pivotally mounted on one end of the fixed contact 22 of the first switch terminal 11, the mounting means comprising a bolt 66, a nut 67 mounted on blade 64, and a bolt head 68 affixed toa crank member 69. Crank 69, which corresponds to crank 39, is pivotally connected to a dual link 73 that is in turn pivotally connected to a clamp lever 74. Clamp lever 74 is affixed to the head 75 of a clamp bolt 76 that extends through the two movable contact blades 64 and 65 and is threaded into a nut 77 affixed to the outer blade 64. The toggle link 73 is aligned with a toggle break post (not shown) like post 56 and is connected to a bias spring (not shown) like spring 51, completing a toggle mechanism for movable contact member 63 that essentially duplicates the toggle for movable contact member 33. A spacer 83 is interposed between the medial portions of blade 64 and 65. A pin 84 extends through the two blades and through spacer 83 and carries a spring 85 that biases the two blades toward each other and into engagement with the spacer 83.

In FIG. 2,-switch 10' is shown in its closed position. To open the switch, bar42 is moved outwardly in the general direction indicated by arrow A, turning counterclockwise about the axis of bolt 36. As the operating bar starts its outward movement, link 43 pulls clamp lever 44 to the left, as seen in FIG. 2, turning the clamp bolt head 45 in a counterclockwise direction and loosening the clamp holding contact blades 34 and 35 in engagement with the outer and inner surfaces of fixed contact 31. This loosening'operation continues, without lifting the blades of movable contact member 33, until the two pivot points for link 43 are approximately in linear alignment with the axis of bolt 45. During this same intervaL-bolt head 38 of clamp bolt 36 is turned in a counterclockwise direction, so that the clamp maintaining blades 34'and 35 in engagement with fixed contact 21 is also released.

When the toggle mechanism comprising link 43 is straightened out as described above, continued outward movement of bar 42 results in counterclockwise pivotal movement of movable contact 33, the axis of pivotal movement being the axisof bolt 36. The free ends of the movable contact blades 34,35 move up wardly away from fixed contact 31, along an arcuate path generally indicated by line B. The same unclamping and toggle alignment operation occurs simultaneously with respect to the second movable contact member 63, so that both contact members move conjointly away from engagement with the fixedcontacts 31 and 32 of the second fixed terminal 23.

Upon closing of the switch, the operations described above are generally reversed. Bar 42 moves the movable contact blades 33 and 63 in a clockwise direction about the pivotal axis defined by the axes of bolts 36 and 66 until toggle link 43 is engaged by post 56 and the corresponding toggle link 73 is engaged by its toggle break post. The posts stop the two links to break the toggle; continued movement of bar 42, in opposition to the direction of arrow A, turns the clamp levers 44 and 74 clockwise to clamp the free ends of the two dualblade contact members to the fixed contacts 31 and 32 of terminal 23. In addition, the final movement of bar 42 to the position shown in FIG. 2 turns both of the clamp bolts 36 and 66 to clamp both of the dual blade movable contact members to the fixed contacts 21 and 22 of terminal member 11.

The inner contact blade 35 of movable contact member 33 includes an integral extension portion 91 that projects inwardly of the free end of blade 35, toward the other movable contact member 63. Similarly, the inner contact blade 65 of movable contact member 63 comprises an extension portion 92 that projects inwardly toward the free end of blade 35. The two extension portions 91 and 92 of blades 35 and 65 are aligned with each other; indeed, the two extension portions of the inner movable contact blades can engage each other at the center of the switch structure.

The extension portion 91 of movable contact blade 35 carries an arcing contact 93 which projects outwardly of the movable contact blade and preferably extends a short distance below the blade, particularly as shown in FIG. 2. The movable arcing contact 93 is aligned with a fixed arcing contact 94 which is mounted upon a leaf spring 95 affixed to the bottom wall 28 of switch terminal 23. The fixed arcing contact 94 is positioned to engage the movable arcing contact 93 upon upward movement of movable contact member 33, maintaining electrical contact after the blades of contact member 33 begin to separate from fixed contact 31. A similar construction is employed on the other side of the switch, movable arcing contact 97 being affixed to the extension portion 92 of blade 65 in alignment with a fixed arcing contact 98 mounted upon a spring member 99 that is electrically and mechanically connected to terminal 23. This arcing contact arrangement is utilized to preclude arcing between the main contact members and thus avoid pitting the other damage to the contact members in normal operation of the switch.

An arc chute 101 is incorporated in switch 10; the arc chute may be omitted if the switch serves essentially as a disconnect switch. The are chute 101 comprises two side frame members 103 and 104 mounted upon the outer side walls 27 and 26, respectively, of the second fixed terminal 23 of the switch. The back wall 105 of the arc chute is supported between the two frame members 103 and 104 of the arc chute, affording a frame around three sides of an arc space encompassing a part of the contact path B immediately above the fixed contacts 31 and 32 of terminal 23. A plurality of metal grid plates 106 extend across the frame between the two side frame members 103 and 104 and afford a plurality of arc-dividing chambers 107 withinthe arc space encompassed by are chute 101.

Preferably, the side frame members 103 and 104 and the back frame member of arc chute 101 are formed of a plastic or similar material which emits a de-.

dentation 112 is also aligned with arcing contacts 97 and 98. As can be seen from FIG. 2, arc chute 101 projects only to a minimum height above fixed terminal 23 and affords a quite-compact configuration with respect to the remainder of the switch.

In switch 10, the two fixed arcing contacts 94 and 97 are disposed only a very short distance ahead of the leading edge 113 of the top wall 25 of terminal 23. As a consequence, the top wall of terminal 23 affords a stop limiting the outward movement of the arcing contacts that can occur upon interruption of a fault current of substantial magnitude. This is accomplished with vno special structure required to provide the stop structure;v

on the other hand, the stop is quite important in preventing damage to the switch if and when it is opened or closed under fault conditions.

Switch 10 is substantially smaller in size and lighter in weight than comparable load break switches as heretofore known in the art. Even at high ampere ratings, the switch is relatively cool in operation. It affords effective and adequate arc protection, even .for opening and-closing of the switch under overload conditions or closing on a fault, with a structure that extends for a minimum height above the conjunction of the movable and fixed contacts of the switch. Upon operation of the switch in the presence of an overload or a fault, the resulting high current are tends to drive the free ends of the inner contact blades 35 and 65 toward each other. However, the blade extensions 91 and 92 engage each other and prevent substantial damage to the switch. The arcing contacts of the switch are located at approximately the same level as the upper wall of the tubular'fixed terminal. 23, maintaining the overall switch height at a minimum. In. general, the switch is smaller, lighter, cooler in operation, and affords less contact resistance than previously known devices of comparable rating, while affording a rugged tact member comprising a pair of contact blades pivotally mounted at one end on opposite sides of one fixed contact of said first terminal, and each movable contact member being movable along an arcuate path between an open position displaced from said second terminal and a closed position in which the free ends of the blades of the contact member engage substantial areas on opposite sides a of one fixed contact of said second terminal;

the inner contact blade of each contact member including an integral extension portion, at the free end thereof, projecting inwardly toward and into close proximity to the corresponding extension portion of the inner contact blade of the other contact member;

and an operating mechanism for moving said contact members, conjointly, between their open and closed positions, and for tightly clamping both blades of each contact member to its associated fixed contacts when in said closed position.

2. A high current switch according to claim 1 and further comprising:

two movable arcing contacts, one mounted on the extension portion of the inner contact blade of each contact member on the side of the extension portion toward the second terminal; and

two fixed arcing contacts, mounted on said second terminal in electrical contact therewith and each aligned with one of said movable arcing contacts for engagement by the movable arcing contact during opening movement of the switch, said fixed arcing contacts each being positioned approximately in alignment with the cut-away portion of the top wall of the second terminal.

3. A high current switch according to claim 2 in which said fixed arcing contacts are resiliently mounted for movement toward and away from the edge of the top wall of said second terminal and in which the top wall of said second terminal affords a stop preventing excessive movement of said fixed arcing contacts in the event that the switch is opened or closed under fault conditions.

4. A high current switch according to claim 1 and further comprising: an arc chute mounted on said second terminal, said arc chute comprising two side frame members mounted on opposite side walls of said second terminal, a back wall mounted between said frame members to afford a frame around three sides of an arc space encompassing a part of both said paths im mediately above the fixed contacts of said second terminal, and a plurality of grid plates extending across said frame between'said two side frame members and forming a plurality of arc-dividing chambers within said are space. a 

1. A high-current switch comprising: a first fixed terminal and a second fixed terminal mounted on a base in spaced relation to each other, each fixed terminal comprising a tubular conductor of generally rectangular configuration and each having a portion of the top wall of the terminal cut away to afford a pair of fixed contacts extending toward and aligned with a similar pair of fixed contacts at the other terminal; two movable contact members, each movable contact member comprising a pair of contact blades pivotally mounted at one end on opposite sides of one fixed contact of said first terminal, and each movable contact member being movable along an arcuate path between an open position displaced from said second terminal and a closed position in which the free ends of the blades of the contact member engage substantial areas on opposite sides of one fixed contact of said second terminal; the inner contact blade of each contact member including an integral extension portion, at the free end thereof, projecting inwardly toward and into close proximity to the corresponding extension portion of the inner contact blade of the other contact member; and an operating mechanism for moving said contact members, conjointly, between their open and closed positions, and for tightly clamping both blades of each contact member to its associated fixed contacts when in said closed position.
 2. A high current switch according to claim 1 and further comprising: two movable arcing contacts, one mounted on the extension portion of the inner contact blade of each contact member on the side of the extension portion toward the second terminal; and two fixed arcing contacts, mounted on said second terminal in electrical contact therewith and each aligned with one of said movable arcing contacts for engagement by the movable arcing contact during opening movement of the switch, said fixed arcing contacts each being positioned approximately in alignment with the cut-away portion of the top wall of the second terminal.
 3. A high current switch according to claim 2 in which said fixed arcing contacts are resiliently mounted for movement toward and away from the edge of the top wall of said second terminal and in which the top wall of said second terminal affords a stop preventing excessive movement of said fixed arcing contacts in the event that the switch is opened or closed under fault conditions.
 4. A high current switch according to claim 1 and further comprising: an arc chute mounted on said second terminal, said arc chute comprising two side frame members mounted on opposite side walls of said second terminal, a back wall mounted between said frame members to afford a frame around three sides of an arc space encompassing a part of both said paths immediately above the fixed contacts of said second terminal, and a plurality of grid plates extending across said frame between said two side frame members and forming a plurality of arc-dividing chambers within said arc space. 